IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Applied Surface Analysis Monday Sessions
       Session AS-MoP

Paper AS-MoP5
Charged Layer Calculation for an Effective Surface/Interface Analysis of Insulating Oxides using AES

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Student Poster Competition/Aspects of Applied Surface Analysis I Poster Session
Presenter: S. Wannaparhun, University of Central Florida
Authors: S. Wannaparhun, University of Central Florida
S. Seal, University of Central Florida
V. Desai, University of Central Florida
K. Scammon, University of Central Florida
Z. Rahman, University of Central Florida
Correspondent: Click to Email
Auger Electron Spectroscopy (AES) can provide compositional information with excellent spatial resolution. Unfortunately, charging problem has known to be a major obstacle for characterizing insulating materials. Four parameters affect the degree of charging phenomenon; (i) resistivity of materials, (ii) primary electron beam energy, (iii) total electron yield, and (iv) sample thickness. First three parameters have been paid attention for overcoming the problem, however the charging problem still exists. Herein, a proposed model to overcome the charging in all insulating materials has found to be successful in analyzing insulating materials. A negatively charged layer will present at the top surface when the insulating material is analyzed using an e-beam. The negatively charged layer thickness is a function of the e-beam energy and other material constants (such as density, average atomic number, and average atomic mass). The accumulated negative charges will dissipate to the ground when the sample thickness is equal or less than the charged layer. Hence, the sample thickness in this case is defined as an effective thickness. Both capacitor and double charged layer models are applied to calculate the effective thickness of insulating materials for Auger analysis without charging. The effective thickness is used as a criterion for sample preparation. Focused ion beam (FIB) technique is utilized to prepare a specimen with the effective thickness as predicted by the model for minimal or no charging during analysis. An oxide/oxide ceramic matrix composite; Nextel 720 fiber/ aluminum oxide for high temperature applications in gas turbine was selected for this study. A thin specimen including an interface between the fiber and the matrix is imaged and corresponding AES spectra are acquired from selected regions with no charging. The results are compared to a thicker sample, which suffered severe charging during AES analysis. The effective thickness for more than fifty solid oxides are also calculated using our model for future AES analysis without charging and is presented in a periodic table format.